Sheet glass apparatus



Sept. 28, 1937. F. R. HOHMANN SHEET GLASS APPARATUS Filady Deo.` 13, 1955 Snventor @FDEP/CK A? Haw/:AHM

' Y Gttorneg Patented Sept. 28, 1937 .SHEET GLASS APPARATUS Frederick R. Hohmann, Charleston, W. Va., as-

signor to Libbey-Owens-Ford Glass Company, Toledo, Ohio, a. corporation of .Ohio

Application December 13,1933', serial No. 102,184

1c (ci. 49-33) The present invention relates broadly to themanufacture of sheet glass and more particularly to an improved method and apparatus for the production of acontinuous sheetor ribbon of 5 glass Aby a rolling operation.

In the production of sheet glass according to.

one well-known process, a pairA of relatively large internally cooled rotatable sheet forming rolls are vmounted side by side above and in close proximity to the surface of a bath of moltenv glass contained within a relatively shallow working receptacle or draw-pot, the said receptacle being continuously 'supplied with molten glass from a tank furnace communicating therewith. The two forming rolls are horizontally spaced from` one another to create a vertical sheet forming pass therebetween and, upon rotation, are adapted to draw a relatively heavy body of glass upwardly from the molten bath and reduce it to a sheet of substantially predetermined and uniform thickness. 'Ihe sheet is continued upwardly for a short disT tance and then deflected over a bending roll into the horizontal plane, said sheet being carried forwardly upon 'a series of conveying rolls which de- 21S-liver it into a flattening chamber from which it passes into and through an annealing leer. It is preferred, in the above process, that the sheet forming rolls be so arran 'c1-that the lower portions of the peripheries t f ereof just contact with the upper surface of the bath of molten glass within the working receptacle, being neither above nor beneath the same but tangent therewith.

-When producing sheet glass in the manner above described it is essential that the molten glass at the point of removal from the working receptacle be maintained at a relatively high temperature and, in fact, at a considerably higher temperture than is necessary in some other processes 40 of forming sheet glass, such as, forexample, in

the well-known Colburn sheet drawingprocess.'

This relatively high temperature is required in order, among other things, to offset the relatively great chilling effect producedby the internally cooled sheet forming rolls, whereby the glass can be maintained at a temperature suiiicient to permit of the drawing up of a relatively heavy body of,y molten glass and the rolling thereof to sheet form. Furthermore, a rolling machine of the above character naturally withdraws a much larger tonnage of glass-from the furnace in a day than does, for instance, the Colburn machine.`

When controlling the operation of the tank furnace, having in mind the supplying ofthe necessary amount of glass at the prop/er temperathrough. I-have discovered that a cooled cylinture to the working receptacle, I have observed thatthere is a tendency for surface seeds and blisters to form upon the top of the molten glass as it flows through the melting and refining portions of the furnace. As is well known, seeds 5 'and blisters are simply air and gas bubbles which form in the glass, and which, if permitted to pass intothe sheet, will result in defects therein.

The laim and'object, therefore, of the present invention resides in the provision of a novel and improved method of and apparatus for effecting the removal of these surface/seeds and blistersv from the glass'prior to thepassage of the glass into the working receptacle to the end that the molten glass within said receptacle will be of an improved quality,lresulting1,r in a sheet relatively free from seeds andgblisters. c

Briefly stated, this is accomplished by the imlmersion of a cylindrical member or roll within the molten glass in advance of. the workin`g\,recep. tacle, said cylindrical member or roll extending 20 transversely of the furnace and being 4positively x driven. The cylindrical member orroll is. also preferably metallic and internally cooled by the circulation of a suitableI cooling medium there- 25 drical member or roll slightly immersed within the molten glass and driven at a peripheral speed relatively greater than the movement of the glass therebeneath acts to elect the breaking up and dispersion of the surface seeds and blisters present upon the top `of the molten glass. This is caused not only by the direct contact of the cooled member or roll with the seeds and blisters (air and-gas bubbles) but also due to the fact 5 that the rotation of the said member or roll results in the disturbance of the surface tension of the glass, causing a stretching of the seeds and ,blisters and the breaking thereof.

Other objects and advantages of the invention will 'become more -apparent during the course of the following description when taken in connection with the accompanying drawing.

In the drawing, wherein like numerals are employed todesignate like partsthroughout the same, j

. Fig.' 1 is a vertical longitudinal section through sheet glass apparatus constructed in accordance with the present invention,

Fig. 2 is a side elevation of a portion thereof, and x Fig. 3 is a horizontal sectional view showing an alternative arrangement.

Referring now to the drawing, 5 designates a relatively shallow working receptacle or drawpot adapted to contain a mass of molten glass 6 which may be continuously supplied thereto from a suitable tank furnace 'I. 'I'he Working receptacle 5 is preferably supported upon stools 8 above a heating chamber 9 heated in any conventional manner. 4

Arranged above the mass of molten glass 6 'Within working receptacle 5 is a pair of sheet forming rolls IU and II respectively mounted with respect to one another to create a vertical sheet forming pass therebetween. 'Ihe rolls are adapted to be positively driven and, upon rotation, are adapted to draw a relatively heavy body of glass I2 upwardly from the molten mass 6 and reduce it to a sheet I 3 of substantially predetermined and uniform thickness. The sheet may be continued I upwardly for a relatively short distance and then deflected over a rotatable bending roll I4 into the horizontal place and carried forwardly upon a series of conveying rolls I5 into and through anvannealing leer (not shown).

In order to assist in properly conditioning the bath of molten glass 6 and to protect the forming rolls and sheet, there is positioned above the Working receptacle 5 suitable cover or-lip tiles I6 and II, which direct heated gases issuing from the furnace 'I and pot chamber 9 downwardly upon the molten glass. Associated with the cover tile Il is a cooler I8 also serving to prevent heat and gases from striking the forming rolls and also from striking and injuring lthe sheet being formed. Arranged at substantially the juncture of the furnace 1 and working receptacle 5 is a jack-arch I9 having its lower end terminating relatively close to but spaced from the surface of the body of molten glass 6 within the furnace.

As stated above, it is desirable that the forming rolls I0 and II be so arranged that the lower portions of the peripheries thereof are located substantially at the surface of the mass of molten glass 6, being preferably neither above nor beneath the same. Also, that in the operation of this type of machine, it is necessary that the molten glass within the receptacle be maintained at a relatively high temperature in order to permit of the properformation of the sheet.

However, in ring and handling the tank furnace in the manner necessary to supply a suflicient quantity of molten glass at the required temperature to the working receptacle, I have observed that there is a tendency for seeds and blisters to form upon the surface of the body of the molten glass as it flows through the furnace to the working receptacle. Obviously, this is an undesirable condition, since the drawing of these seeds and blisters into the glass sheet will naturally result in defects therein.

The primary purpose of this invention, therefore, lies in the provision of means for breaking up these surface seeds and blisters before the glass flows into the working receptacle. To this end, there is provided a preferably metallic cylindrical member or roll 20 extending transversely the entire width of the furnace and being slightly immersed within the body of molten glass 6 in advance of the working receptacle. For instance, the roll 20 may be positioned relatively closely adjacent the jack-arch I9 at the side thereof adjacent the working receptacle, as illustrated in Fig. 1, or at the opposite side of the jack-arch as shown in Fig. 3. The roll 20 is hollow and preferably internally cooled by the circulation of a suitable cooling medium therethrough.

The roll 20 is provided at its opposite ends with the reduced end portions 2l which project through vertical slots 22 (Fig. 2) formed in the refractory blocks 23 arranged at opposite ends of the cover tile I'I, said end portions being rotatably mounted in bearing blocks 24 which are slidably received between spaced vertical posts 25 and 26 carried by a base plate 21 secured to a horizontal supporting member 28. Fastened to the upper end of each bearing block 24 is a horizontal bar 29 through which are vertically threaded screws 30, the lower ends of which rest upon the tops of the posts 25 and 26. With this construction, it will be readily apparent that the roll 20 can be readily raised or lowered to vary the depth of immersion thereof within the molten glass by simply rotating the screws 30 in the proper direction. The roll 20 is also adapted to be positively driven, such as by means of a chain and sprocket drive or the like 3| (Fig. 3).

I have discovered, by actual practice, that the use of the internally cooled metallic roll 20 seems to effect the breaking up and dispersion of the surface seeds and blisters present upon the top of the molten glass as they are carried therebeneath.' The breaking up of these surface seeds 2 and blisters which, as pointed out above, are

simply air and gas bubbles, is due not only to the direct contact of the cooled roll with the said seeds and blisters but also to the disturbance of the surface tension of the glass. In other words, since the roll is being rotated at a peripheral speed relatively faster than the speed of movement of the glass therebeneath, the said roll tends to stretch the upper layer of glass, therefore increasing the surface tension thereof, and causing the breaking of the air and gas bubbles.

It is to be understood lthat the form of the invention herewith shown and described is to be taken as the preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit o f the lnvention or the scope of the subjoined claims.

I claim:

1. In sheet glass apparatus, a Working receptacle containing a mass of molten glass, a furnace in communication with said receptacle for supplying the molten glass thereto, a pair of rotatable forming rolls arranged side by side above the working receptacle and adapted, upon rotation, to draw a body of molten glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries thereof are disposed substantially at the surface of the mass of molten glass, a movable metallic member extending transversely of the furnace in advance of said forming rolls and being immersed to a uniform depth throughout the width of the mass of molten glass therein for effecting the breaking up of surface seeds and blisters present upon the glass,v

and means for cooling said movable metallic member to prevent the molten glass from sticking thereto.

2. In sheet glass apparatus, a working receptacle containing a mass of molten glass, a furnace in communication with said receptacle for supplying the molten glass thereto, a pair of rotatable forming rolls arranged side by side above the'working receptacle and adapted, upon rotation, to draw a body of molten glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries thereof are disposed the working'receptacle and adapted, upon rotasubstantially at the surface of the mass of molten glass, a rotatable metallic member extending transversely of the furnace in advance of said forming rolls and being immersed to a uniform depth throughout the Width of the mass of molten glass therein for effecting the breakingup of surface seeds and blisters present upon the glass, and means for cooling said rotatable metallic 4member to prevent the-molten glassrfrom sticking thereto.

3. In sheet glass apparatus, a working receptacle containing a mass of molten-glass, a furnace in communication with said receptacle for supplying the molten glass thereto', a pair of rotatable forming rolls arranged side by side above the working receptacle and adapted, upon rotation, to draw a body ofmolten glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries thereof are disposed substantially at the surface of the mass'of molten glass, a rotatable cylindrical metallic member eXA tending transversely of the furnace in advance of said forming rolls and being immersed to al uniform depth throughout the width of the mass of molten glass therein for effecting the breaking up of surface seeds and blisters present upon the glass, and means for internally cooling said rotat-I able cylindrical metallic member to prevent the molten glass from sticking thereto.

4. In sheet glass apparatus, a worklng re' ceptacle containing a massl of molten glass, a

furnace in communication with said receptaclen for supplying the molten glass thereto, a pair of rotatable forming rolls arranged side by side above the Working receptacle and adapted/upon rotation, to draw a relatively heavy body of molten glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries thereof are disposed substantially at the smface A of the mass of molten glass, a rotatable metallic roll extending transversely of the furnace in advance of said forming rolls, said rotatable roll being of a uniform diameter across the width of the furnace and being immersed within the mol-C ten glass therein for effecting the breakingup of surface seeds and blisters present upon the glass,

and means for cooling said roll to prevent the molten glass from-.sticking thereto.

5. In sheet glass apparatus, a-working receptacle containing a mass of molten glass, a furnace in communication with said receptacle for supplying -the molten glass thereto, a-pair of rotatable-forming rolls arranged lside by side above the working receptacle and-adapted, upon rotation, to draw a relatively heavy body of molten glass upwardly from said mass and reduce it to sheet formmsaid forming rolls being so arranged that the` lower portion of the peripheries thereof are `disposed substantially at the surface of the mass of molten glass, a rotatable cylindrical me- -tallic member extending transversely of the furnace in advancepf said forming rolls and being immersed to a uniform depth throughout the width of the mass of molten glass therein for effecting the breaking up of surface seeds and blisters present upon the glass, and means i'orV` cooling said cylindrical member to prevent the molten glass from sticking thereto. 6. In sheet glass apparatus, a working receptacle containing a mass of molten glass, a furnace blisters present upon the glass, and means for plying the molten glass thereto, a pair of rotatable forming rolls arranged side by side above tion, to draw a relatively heavy body of molten glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries there .of are disposed substantially at the surface of the mass of molten glass, arrotatable metallic roll extending transversely of the furnace in advance of said forming rolls, said rotatable roll tacle containing a mass of molten glass, a furnace in communication with said receptacle for sup-v plying the molten glass thereto, a pair of rotat-- able forming rolls arranged side by side above the working receptacle and adapted, upon rotation, to draw .a relativelyheavy body of molten glass upwardly, from said mass and yreduce it to sheet form, said forming rolls being so arranged thatr the lower portions of the peripheries thereof are disposed substantially at the surface of the mass of molten glass, a rotatable cylindrical metallic member extending transversely of the furnace in advance of said forming rolls and being immersed to a uniform depth throughout the width of the mass of molten glass therein for effecting the breaking up of surface seeds and blisters present upon the glass, means for cooling said cylindrical member to prevent the molten glass from sticking thereto, and means for mounting the within the molten glass.:

8. In sheetglass apparatus, a working receptacle containing a mass of molten glass, a furnace in communication with said receptacle for supplying the molten glass thereto, a pair of rotatable forming rolls arranged side by side abovegthe working receptacle and adapted, uponv rotation, to draw a relatively heavy body of moltenv glass upwardly from said mass and reduce it to sheet form, said forming rolls being so arranged that the lower portions of the peripheries thereof are disposed substantially at the surface of the mass of molten glass,a rotatable metallic roll extending transversely of the furnace in advance of said forming rolls, said rotatable roll being of a uniform diameter across the width of the furnace and being immersed within the `molten glass therein for effecting the breaking up of surface UlA seeds and blisters present upon the glass, means for internally cooling said roll to prevent the molten glass from sticking thereto, and means for mounting the roll so that itv can be adjusted vertically to vary the depth of immersion thereof within the molten glass.'

9. In the method of forming continuous sheet glass, wherein molten glass is continuously flowed 10 pair of rotatable rolls and reduced thereby to sheet form, in breaking up the surface seeds and blisters present upon the glass before the glass reaches the point of sheet formation byimmersing an articially cooled heat absorbing body within said mass and to a uniform depth across the width thereof, and in continuously revolving said heat absorbing body to cause a disturbance of the surface tension of the glass passing therebeneath while preventing the molten glass from sticking thereto.

FREDERICK R. HOHMANN. 

